////////////////////////////////////////////////////////////////////////////
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////////////////////////////////////////////////////////////////////////////

#include "Types.h"
#include "NgramLM.h"
#include "Mask.h"
#include "Smoothing.h"
#include "MaxLikelihoodSmoothing.h"

////////////////////////////////////////////////////////////////////////////////

namespace mitlm {

Smoothing::~Smoothing() { }

////////////////////////////////////////////////////////////////////////////////

void
MaxLikelihoodSmoothing::Initialize(NgramLM *pLM, size_t order) {
    assert(order != 0);
    _pLM = pLM;
    _order = order;
    _effCounts.attach(_pLM->counts(_order));
}

bool
MaxLikelihoodSmoothing::Estimate(const ParamVector &params,
                                 const NgramLMMask *pMask,
                                 ProbVector &probs,
                                 ProbVector &bows) {
    if (!_estimated) {
        const CountVector &counts(_pLM->counts(_order));
        const IndexVector &hists(_pLM->hists(_order));

        // Compute inverse of sum of adjusted counts for each history.
        CountVector histCounts(_pLM->sizes(_order - 1), 0);
        ProbVector  invHistCounts(histCounts.length());
        BinCount(hists, histCounts);
        invHistCounts = 1.0 / asDouble(histCounts);

        // Compute maximum likelihood probability.  0 backoff.
        probs = counts * invHistCounts[hists];
        bows.set(0);
        _estimated = true;
    }
    return true;
}

}
